Today, Nintendo's Satoru Iwata has said that work for Wii's successor begun the minute the last system was completed and released. Although he said that, I don't expect to see the Wii 2 shortly, as he explained to investors today that there is still plenty of work to do on the Wii as it is.
Speaking at a Q&A session that was held recently, he stated, "as soon as a new system is complete - from the very moment it is complete - we're thinking about the plan for the next game machine." He then went on to say "We believe there's still more we can do with the Wii."
Again, I don't expect we'll see the next Wii at this year's E3, but it's good to know Nintendo have started the development of the successor to the Wii.
http://www.baxy-z.com/site_content.php?title=nintendo-has-begun-planning-wii-2